Vacuum-pump.



J. ZBITLIN.

VACUUM PUMP.

APPLICATION FILED MAR.19,1910.

Patented Aug. 5, 1913.

2 SEEETSSHEET 1.

3 W %/m JW 5 Q Y N 6 6 J ZEITLIN.

VACUUM PUMP.

APPLICATION FILED MAR. 19, 1910.

chamber-may be lubricated without the use cairn s ra rnis JOSEPH zEI'rLm, oF-sonmn KENSING'LON,. LONDON, ENGLAND.

vaeunmrunr.

.1 69,510. p t n- To all whom, it may concern:

Be it known that I, JosnPn'ZnrrLiN, a subject of the Emperor of Russia, residing at 5 (illslOn road, South Kensington, in'the county of London, England, engineer, have invented a'certain new-and'useful Improved Vacuum-Pump, of which the following isa specification. iv

This invention relates to piston vacuum pumps and consists in certain improve ments, the chief of which is the'el imination of all clearance space at the end of the delivery stroke of the pump piston firstly by using an elastic connectionrbetween the pis ton and the actuating mechanism so that the piston can be driven against theend o'fthe cylinder and secondly by'providing an auxiliary piston or plunger which fills'the port in the cylinder head through which the gases are expelled after the deliverystroke of the main piston has been completed.

In the production of very high and pure 3 vertical section i 1, Fig. 3 adetailillustrating the valveactuvacua, such as for example'the vacuum re- (hired in incandescent electric lamp bulbs,

it is necessary or advisable to inclose the pump or preferably two or more pumps connected in series, in an evacuated chamber and the invention will be hereinafter described with reference to a vacuum pump. which is so inclosed, but it will be understood that in so far at any rate as the chief features of the improved pump are concerned, it may be applied to apparatus which is not so inclosed. f i

In the specification to United States Patout No. 905973 granted to-the present-a1} plicant it is stated with reference to'the-multiple stage pump apparatus forthe production of high vacu-a that by placing the'high vacuum pumps in one vacuum chamber and the preliminary exhaustion pumps with the motor for driving all the pumps in asecond vacuum chamber, the apparatus in-the first of liquid lubricants-so that the high vacuum chamber may be free from thevapor of suchlubricants, but'according to this invention the pump is so' constructed that no lubricant of any sort whatever-need be used for the pump cylinders or pistons or dist-rihutin-g valves and preferably also although 'notnecessarily without any lubricant for any of the parts inclosed within the chamber aforesaid, the parts subject to rubbing friction being constructed so as tobe substanpair of ball bearings tially frictionless and" immunity from leakremn n ratenseaau isnaiei mm. serial No; 551x458.-

age being obtained by making the leakage surfaces of'great length. Further, special means are provided for eliminating the clear-aims space" of the pump cylinders while leaving ample port area for the admission and discharge ofthe gases to be exhausted. The invention further includes a-doubly elastic connecting rod through which the pump pistons-are actuated from a crank on a'driving shaft, a link motion connecting the'connecting rod with the pistons, a special mechanism for actuatin the distributing valves, and special sea ing ilevices to prevent leakage at the pipe connections and fiomthe atmosphere to the chamber.

These and other improvements will be more particularly described with reference to the accompanying drawings which show a two cylinder series pump inclosed in a chamber which is itself exhausted. by an auxiIiary-pumpnot shown in the drawings, Figure 1 being a sectional plan, Fig. 2 a taken on line 11-11 of'Fig.

ating' mechanism,

shown in Fig. 3.

In these drawings the pumps A, B 1n' closed 'in the casing or chamber C are'driven from a shaft 1 extending through a special stufiing box in'the casing and journaled in a 2, 3. of known kind one within and one outside't-he stufling'box. A beltpulley 4 on the outer end of the shaft provides means for driving the shaft from all-electric or other suitable motor external to-the casing. A ballwasher 5 ofknown type is interposedbetween a collar fixed on the shaft and a suitable-abutment on the casingto take any'inward thrust to Whlchiille shaft may be subject. Leakage from the atmosphere'alongthe shaft into the chamber G'is prevented first by a stufiing b ox;6 fi'lled with-grease which'is retained within the stufiing boxby suitably shaped leather or dermatitis packing members 6, 6",-and secondly by'one or more-somewhat elonegated sleeves '-7 preferably of antifrlction metal whichc'loseIy fit around hardened enlargielments 8 onthe shaft-which are ground to e hereof the sleeves. The-sleeves 7 havetheir inner ends formed with annular bearin members or projections 7 which are urged carefully shoulders of the adjacent into close contact with the-opposing- 1 vation 'of theconnectingirod (detached) and Fig. '5 is an elevation of the mechanism ifdesired be connected with an auxiliary ex-' I which the crank 14 ingly shaped opening in the casing C. The.

space between the dermatine rings 13 may hausting device to minimize the chance of leakage into the chamber C. Y t i The shaft 1 is geared with a shaft 14 from pump pistons are driven by a t rough a linkage comprising a divided .connect-ing'rod the two parts 15, 16 of which are relatively movable in the direction of their axes and are correlated by means of a' airof springs 17, 18 which are compressed tween follower plates 17, 17 and 18, 18 of which the plates 17, 18 are adjustably secured on the part 16 of the connecting rod, while the plates 17 18 are loose on this part ofthe rod and bear against suitably shouldered abutments on the part 15 of the rod. The part oi the rod 16 marked 16 which slides in a bush 15" in' the part '15 is of enlarged diameter for the reason afterward explained and to. avoid v 19 fixed on a rock shaft 19 on which also is any shake the bush 15 is made equal or very slightly longer than the part/16. It .Wlll be seen that this connecting rod is substantially rigid so long as no axial force-is applied exceeding that due to the compres sion of the spring that is for the time re sisting the force being applied and that it will be extended or shortened as the case may be when subjected to a greater force,

the very slight difference in the lengths of the parts 15, 16 being taken up by the almost inappreciable relative movement of the two parts of the connecting rod when the latter is subject to a thrust or pull. The other spring that is to say the non-resisting spring, is rendered inoperative, as it abuts against the shoulder of the part 16*.

The connecting rod 15, 16 couples the crank 14 with the end of an arm or crank rigidly fixed a bell crank 19', 19. The

crank arm 19 is coupled indirectly with the main piston of :pump B through the con-' nectmg rod 20 which is directly connected with an auxiliary zpiston or'clearance plunger 21 the object of which will be hereinafter explained. Similarly the crank arm 19"is coupled indirectl with the main'pistonof pump .A throug link'22, bell crank 23 on rock shaft 23 which is oppositely disposed to'b'ut is otherwise the duplicate of 19 and 19, and. connecting rod 20-which,

latter is directly coupled with the auxiliary piston 21 of pump A. l The linkage'connecb ing the rock shaft 19' with the two pistons is so designed that the oppositely moving pistons are always in substantial balance.

The auxiliary pistons 21 are mountedwithin the elongated cored bosses 24 ofthe main pistons 24 within which they have a limited freedom longitudinally, the laterallyextending pins 21" at the loweriend of the pistons 21 sliding in longitudinal slots 24?'1 n the sleeves 24. A spring 25 compressed betwen the main piston 24 and a j follower plate 21 carried by the pins 21' tends tokee the auxiliary piston with drawn .into t e boss 24. as shown in pump B (Fig; 2)., in which position the rear. face the end of the boss 24, with a small cleanance left between the pins 21 and the end of the slot 24". The auxiliary pistons 21 have projecting pieces 21 which are shaped to fillexactly the ports 27 in the cylinder head connecting the interior of the cylin-' force the auxiliary plstons to close completely the ports 27, the pistons and their actuating linkage remaining stationary in this position for a period during whichthe crank 14* passes over the dead point.

The valve plugs 28 are oscillated inter-j mittently so as to bring the suction ducts 28v and dischargeducts' 28 into register with the ports 27 at the appropriate times by means of pinions 29 on-the plug spindles 29 which mesh respectively with two toothed wheels 30 gearing *with each other and carried by stub shafts 30 journaled in a bracket 31 integral with the pedestal of the crank shaft 14. The gear wheels 30 F igs'. 3 and 5 are actuated intermittently by means of a tappet 32 on the crank shaft 14. As

the tappet' rotates a, projection 32 on its free end is adapted to pass into and out of engagement successively with the projections 3O 'on the faces of the gear wheels and turn the wheels as long as thetappet projection 32* and either of the projections 30", which maybe in engagement withit, are moved along the same path. It will be seen by reference to Fig. 3 thatduring the periods of engagement the two wheels 30 will be rotated alternately in opposite directions and consequently the valve plugs with which the wheels 30 are geared will be oscillated intermittently. In order that this movement of theplugs should be accelen ated the gear wheels 30 are connected by tension springs indicated by the arrows 33 which tend to turn the wheels inward to ward each. other in one direction or the other depending upon which side of the line 80 of the plate 21'? bears against a stop 26 on a the latter. The angular relation of the tappet 32 and the crank 14 is such that the movement of the Wheels 30 by the t-appet 32 begins a little before the crank 14? passes the dead point and the whole movement of the valves is completed during the time that 3 the main pistons and the auxiliary pistons. and their operating linkage are stationary; and the double elastic connecting rod 15, 16 E is being extended or shortened. In other? words the angle through which the tappeti 32 has to move in order that the shifting of theval-ves should be begun and completed. is less than the angle through which the crank 14 sweeps during the period of inacl The suction duct 28" tion of thepistons. of the valve of pump A is connected with the vessel to be exhausted. by a pipe 36 connected with an external stop cook 37 which is secured gas tight in the wall of the chamher 0. The delivery duct- 28" of the valve of pump A is connected by a pipe 38 with the suction duct 28 of the other valve the delivery duct of which may open into the chamber C as shown or may be connected with the suction' port of an external exhausting pump, or with an external evacuated space, by a pipe or duct 47 passing gastight through the wall of the chamber.

The valve plugs 28 are conical fitting in conical sleeves 39 which have at their two ends cylindrical parts 39 which house the ball bearings 40 on which the plugs 28 are mounted. Leakage at the junctions of the pipes 36, 88 and the valve plug spindles is prevented by means of a device similar to that already described in connection with the shaft 1. At each of these junctions a '1 spring 41 incompression between a fixed i which for-ms part bracket or abutment 42 and a flange 43 on the ends of the pipes 86, 38 forces an annular bearing ring 43 on the face of the flange against the carefully ground face either of a fixed shoulder'on the valve plug spindle 29, or, in the case of the suction end of the valve of pump A, of an extension piece or hollow nut 44 which is screwed on the end of the spindle 29 against the flange45 of a sleeve 45 (with suitable interposed packing) of a double ball thrust washer of known. type, the central washer 46 of which is rigid with the shell of the valve. In assembling the parts the screw-threaded end of the plug spindle 29 is screwed into the sleeve 45 of the double ball thrust washer until the plug 28 is in sufficiently close contact with the shell 39 and the nut 44 is then screwed on the end of the spindle to lock the parts. A similar double ball thrust washer is provided at the delivery end of the valve pump B. By providing the plug valves with ball thrust washers as described the adjustment of the plug is accurately maintained in spite of any unbalanced force acting in an axial direction on the plugs.

Apart from the special anti-leakage devices hereinbefore described the tendency to leakage is minimized by lengthening the leakage surfaces as much as possible, this being of course particularly necessary in the case of the pistons both main and auxiliary, neither of which are lubricated either with oil or even any dry lubricant, the small difference of pressure on the two sides of the piston due to the use of the evacuated chamber enabling a comparatively frictionless piston to be used and lubrication dispensed with. The fixed joints, such as the covers of the chamber and of the cylinders may be made in any suitable known manner.

Having thus described the nature of my said invention and the best means I know of carrying the same into practical effect, I claim 1. In vacuum pumps, a pump cylinder, a port in the cylinder end, a main piston within the cylinder, an auxiliary piston mounted within the main piston and having an end shaped to fit exactly the said port, means normally operating to cause the auxiliary pistonto enter the main piston to a desired extent and means for driving said pistons simultaneously and moving the auxiliary piston independently of and further than the main piston so that the said end of the to fit exactly the port in the cylinder, an

elastic driving connection between the shaft and one ofthe pistons operatingto drive the main piston forward against the cylinder head and to cause the end of the auxiliary piston to fill the port at the completion of the forward or delivery stroke and means interposed between the main and auxiliary pistons and adapted to retain the latter entirely withdrawn within the former until the main piston completes its delivery stroke.

3. In apparatus for producing a high vacuum, a driving shaft, a pump cylinder. a port in the cylinder end, a main piston with- .in the. cylinder, an auxiliary piston mounted within the main piston, a driving connection elastic in one direction between the said pistons, a doubly elastic driving connection between the driving shaft'and one of the pistons whereby the main piston may be driven against'the end of the pump cylinder and --means for projecting the head of the auxiliary piston so as to fill the said port for an appropriate period after the main has completed its delivery stroke.

4. In apparatus for-producing a high and pure vacuum in a vessel, a casing forminga piston closed chamber, a driving shaft extending through the wall of the casing into the chamber, a pump cylinder inclosed in the chamber and having a single port serving for induction and exhaust purposes and adapted to be connected alternately with the vessel and with the chamber, a main piston in the cylinder,.mechanism for actuating the piston, an

. elastic connection between the main piston and -the actuating mechanism whereby the piston may be driven forward against the cylinder end, an auxiliary piston mounted within the main piston, means for projecting the head of the auxiliary piston so as to fill the said port for an appropriate period after the mam piston has completed itsforward movement, and a driving connection between the actuating mechanism and the driving shaft.

5. In apparatus for producing a high and pure vacuum in a vessel,- a casing forming a closed chamber, a driving shaft extending through the wall'of the casing into the chamber, a pump cylinder inclosedin the chamber and having a single port serving for induction and exhaust purposes and adapted to be connected alternately with the vessel and with 'the chamber, a main piston in the cylinder, a crank shaft within the chamber, linkage for actuating the piston, a doubly elastic driving connection bet-ween the crank shaft and the linkage whereby the piston may be driven forward against the cylinder end, an auxiliary piston mounted within the main piston, means for projecting the head of the auxiliary piston so'as-to fill the said port for an appropriate period after the.

limited freedom longitudinally within. the

mam piston, and means for driving the mainpiston through the auxiliary piston..

7. In apparatus for producing a high and pure vacuum in'a vessel, a casing forming a closed chamber, a driving shaft extending through the wall of the casing into the charm "beryapumpcylinder inclosed in the chamber and having a single port 'servinglufor inductionand exhaust purposes and adapted lt be connected alternately with the vessel and v with the chamber, an elongated main piston in the cylinder, an auxiliary piston mounted 4 Within the main piston with a limited freedom longitudinally, a driving connection elastic in one directiondaetween the said piston whereby the head of the auxiliary piston may be projected beyond the head of the main piston for filling the said port, a crank shaft within the chamber and coupled with the driving shaft, a crank on the crank shaft,

linkage for actuatingthe auxiliary piston,-

and a doubly elastic driving connectlon between the crank and the linkage to permit the mainpiston to be driven forward against the cylinder end and to remain stationary for a period during which the crank passes over a dead point.

8. In apparatus for producing a high vacuum, a plurality of pump cylinders connected in series, a .port in the-end of'each cylinder, a valve shell attached to each cylindersend, an oscillati valveplug movably mounted in each she I having a suction duct and delivery duct adaptedto continunic'ate with the respective cylinder port, and means for rotating the valve plug mtermittently and alternately in opposite directions so that the ducts therein register with the respective cylinder ports.

9. In' apparatus for producing a high and pure vacuum in a vessel, a casing forming a closed chamber, a driving shaft extending through the wall of the casing into the chamber, a plurality. of pump cylinders in the. chamber and connected in series, a port -in'the end of each cylinder, a valve shell at.

the end of each cylinder, an oscillating valve .plug movably mounted in each valve shell having a suction duct and a delivery duct adapted to communicate respectively and successively with the corres onding cylinder port, an elongated piston in each cylinder, mechanism for actuatin the pistons for withdrawing air or gas om the vesseland for delivering the air or gas into the chamber, a device for oscillating the valve plugs,-.

and a driving connection coupling the actuating mechanism and the oscillating device. to the driving shaft. I p v 10. In apparatus'for producing a high and pure vacuum in a'vessel, a 'casin forming a closed chamber, a 'drivmgflsha t extendmg throughfthe wall ofthe casing into the chamber, a plurality of pump cylinders in the chamber and connected in series, a port in the end of each. cylinder, a valve shell at the end of each cylinder, an oscillating valve plug movably mounted in each valve shell having a suction duct and, a, delivery duct adapted to communicate respectively andv successively with the corresponding cylinder 'port, an elongated piston m each cylinder,

acrank shaft, a rock shaft, a doublyelastic driving connection between the crank shaft weave and rock shaft, linkage connecting the said rock shaft and the pistons and adapted to cause the pistons to move simultaneojusly in opposite directions, a device for oscillating the valve plugs, and a driving connection coupling the crank shaft and the oscillating device with the driving shaft.

11. In apparatus for producing a high.

crank on the rock shaft, a doubly elastic connecting rod coupling the crank shaft and the crank on the rock shaft, a two-arm bell crank fixed to the rock shaft, a connecting rod coupling one arm "of the bell crank with one of the auxiliary pistons, a second rock shaft within the chamber, a second two arm bell crank fixed to the second rock shaft, a second connecting rod coupling one arm of the second bell crank to the other auxiliary iston, and a link connecting the second arm of the first bell crank with the second arm of the second bell crank.

12. In apparatus for producing a high vacuum comprlsing one or more pumps 1nclosed in a chamber, which pumps are actuated by a driving shaft and have each a conical distributing valve plug provided with suction and discharge ducts adapted to be brought into register with a port in the respective pump cylinders connected therewith, a pair of toothed wheels mounted within the chamber intermediate of the plug spindles and gearing with each other, a pinion on each plug spindle meshing respectively with the toothed wheels and means coupled with the driving shaft for rotating the said toothed wheels intermittently and alternately in opposite directions whereby the said suction and discharge ducts are brought into register with the respective cylinder port.

-13. In apparatus for producing a high vacuum comprising one or more pumps 1nated by a driving shaft closed in a'chamber, which pumps are actuand have each a conical distributing valve plug provided with suction and discharge ducts adapted to be brought'into register with a port in the respective pump cylinders connected therewith, a pair of toothed wheels mounted within the chamber intermediate of the plug spindles and gearing with each other, a pinion on each plug spindle meshing respectively with the toothed wheels, a projection on the face of each wheel, a second shaft a "driving shaft extending coupled with the driving shaft, and a tappet carried by the second shaft and adapted to engage successively the said projections and thereby rotate the said toothed wheels and valve plugs intermittently and alternately in opposite directions so that the said suction and discharge ducts are brought into register, respectively, with a cylinder port.

14;. In apparatus for producing a high vacuum comprising two pumps inclosed in a chamber, which pumps are actuated by a driving shaft and have each a conical distributing valve plug provided with suction and discharge ducts adapted to be brought into register with a port in the respective pump; cylinders connected therewith, a pair of toothed wheels mounted within the chamber intermediate of the plug spindles and gearing with each other, a pinion on each p us toothed wheels, a projection on the face of each wheel, a second shaft coupled with the driving shaft,- a tappet carried by the second ha en adapt d o ngage succe sivel the said p .ojections and threbyrotate 'the said toothed Wheels and valve plugs intermittently and alternately in opposite directions so that the said suction and discharge ducts are brought into register, respectively, with a cylinder port and means whereby the rock- 1ng be accelerated with respect to the rotary movement of the driving shaft.

15. In apparatus for producing a high vacuum comprising a pump provided with a distributing valve plug having a scrcwthreaded spindle. the plug being mounted in a shell and cooperating with a port in the end of the cylinder, means for positively adjusting the plug in an axial direction with respect to the shell and fixing the same in position, comprising a double thrust washer mounted immovably in an axial direction within the shell and internally threaded for the adjustable reception of the said spindle and a nut in screwing adjustment on the said spindle and adapted to be screwed into locking engagement with the washer.

16. In apparatus for producing a high and pure vacuum, a' casing forming a closed chamber, a piston pump within the chamber, mechanism for actuating the pump piston, a driving shaft provided with a plurality of enlargements forming shoulders thereon, the said shaft extending through the wall of the casing in the chamber, a driving connection between the driving shaft and the actuating mechanism, and a device for preventing leakage of air or gas into the chamber along the shaft comprising a stufling box surrounding the shaft, annular packing members for retaining grease within the stufling box, a plurality of elongated sleeves fitting the said shaft enlargements, and springs interposed between the wall of the spindle meshing respectively with the,

movements imparted to the plugs mayv ber, mechanismfor actuating the pump piston, a driving shaft provided with a plurality of enlargements forming shoulders thereon, the said shaft extending through the wall of the casing in the chamber, a

driving connection between the driving shaft and the actuating mechanism, and a device for preventing leakage of air or gas into the chamber along the shaft comprising a stufiing box surrounding the shaft, annular packing members for retaining grease within the stuffing box, a plurality of elongated sleeves fitting the said shaft enlarge ments, springs interposed between the wall of the 'stufiing box and the sleeves and adapted to press the sleeves against the said shoulders, flexible rings interposed between the said sleeves and the wall of the stufiing box and Washers interposed between the stufiing box wall and the sleeves and adapted to retain the rings in proper position.

18. In apparatus for producing a high vacuum, a driving shaft, a pump cylinder, a port in the cylinder end, a main piston within the cylinder, an auxiliary piston mounted within the main piston, a drivingconnection elastic in one direction between the said pistons and means for projecting the head of the auxiliary piston so as to fill the said port for an appropriate period after the main piston has completed its delivery stroke.

In testimony whereof I have signed my name to this specification in .the presence of two subscribing witnesses Witnesses:

JOSEPH MILLARD, WALTER I. SKERTEN.

JOSEPH ZEITLIN. 

